[SeaBIOS] Re: [PATCH v2 4/4] only enable 64bit pci io window when RAM >64G

[Igor Mammedov]

On Wed, 19 Jun 2024 11:21:14 +0100
John Levon  wrote:
> Older 32-bit Linux VMs (including Ubuntu 16.10) have issues with the
> 64-bit pci io window, failing during boot with errors like:
>
> virtio_balloon virtio2: virtio: device uses modern interface but does not have VIRTIO_F_VERSION_19734-565debf7b362
> virtio_net virtio0: virtio: device uses modern interface but does not have VIRTIO_F_VERSION_1
> Virtio_scsi virtio1: virtio: device uses modern interface but does not have VIRTIO_F_VERSION_1

above aren't exactly indicate 64-bit MMIO window as culprit

Can you provide more data on what exactly goes wrong and where?

Does adding 'realloc' option to guest kernel CLI help?
> Gave up waiting for root device.  Common problems:
> Boot args (cat /proc/cmdline)
> Check rootdelay= (did the system wait long enough?)
> Check root= (did the system wait for the right device?)
> Missing modules (cat /proc/modules; ls /dev)
>
> ALERT!  /dev/disk/by-uuid/86859879-3f17-443d-a226-077c435291e2 does not exist.
> Dropping to a shell!
>
> Be a bit more conservative, and only enable the window by default when
> the ram size extends beyond 64G - a 32-bit guest using PAE cannot
> address beyond that anyway. Due to the mmio window this translates
> to an effective working configuration limit of 62G/63G, depending on
> machine type.
>
> Fixes: 96a8d130 ("be less conservative with the 64bit pci io window")
> Signed-off-by: John Levon
>
> src/fw/paravirt.c | 28 ++++++++++++++++++++++++----
>  src/fw/paravirt.h |  1 +
>  src/fw/pciinit.c  |  6 +++++-
>  3 files changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 3ad9094b..5b0f191b 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -29,11 +29,14 @@
>  #include "stacks.h" // yield
>
> #define MEM_4G (0x100000000ULL)
> +#define MEM_64G (16 * 0x100000000ULL)
>
> // Amount of continuous ram under 4Gig
>  u32 RamSize;
>  // Amount of continuous ram >4Gig
>  u64 RamSizeOver4G;
> +// Amount of continuous ram >64Gig
> +u64 RamSizeOver64G;
>  // physical address space bits
>  u8 CPUPhysBits;
>  // 64bit processor
> @@ -591,8 +594,12 @@ qemu_cfg_e820(void)
>                  | ((u32)rtc_read(CMOS_MEM_HIGHMEM_MID) << 24)
>                  | ((u64)rtc_read(CMOS_MEM_HIGHMEM_HIGH) << 32));
>      RamSizeOver4G = high;
> RamSizeOver64G = 0;
> if (high + MEM_4G > MEM_64G)
>    RamSizeOver64G = high + MEM_4G - MEM_64G;
> e820_add(MEM_4G, high, E820_RAM);
>    dprintf(1, "RamSizeOver4G: 0x%016llx [cmos]\n", RamSizeOver4G);
> dprintf(1, "RamSizeOver64G: 0x%016llx [cmos]\n", RamSizeOver64G);
>
> }
>
> // Populate romfile entries for legacy fw_cfg ports (that predate the
> @@ -774,19 +781,32 @@ static int qemu_early_e820(void)
>              e820_add(table.address, table.length, table.type);
>              dprintf(1, "qemu/e820: addr 0x%016llx len 0x%016llx [RAM]\n",
>                      table.address, table.length);
>        // address below 4g?
>        if (table.address < MEM_4G) {
>            // below 4g
>            if (RamSize < table.address + table.length)
>                RamSize = table.address + table.length;
>        } else {
>            // above 4g
>            if (RamSizeOver4G < table.address + table.length - MEM_4G)
>                RamSizeOver4G = table.address + table.length - MEM_4G;
>            u64 table_end = table.address + table.length;
>            /*
>             * Note that this would ignore any span that crosses the 4G
>             * boundary. For RamSizeOver64G, we do account for any spans
>             * that cross the 64G boundary.
>             */
>            if (RamSizeOver4G < table_end - MEM_4G)
>                RamSizeOver4G = table_end - MEM_4G;
>            // crosses 64G ?
>            if (table_end > MEM_64G) {
>                if (RamSizeOver64G < table_end - MEM_64G)
>                    RamSizeOver64G = table_end - MEM_64G;
>            }
>        }
>    }
>
> }
>
> dprintf(1, "qemu/e820: RamSize: 0x%08x\n", RamSize);
>    dprintf(1, "qemu/e820: RamSizeOver4G: 0x%016llx\n", RamSizeOver4G);
>
> dprintf(1, "qemu/e820: RamSizeOver64G: 0x%016llx\n", RamSizeOver64G);
> return 1;
>
> }
> diff --git a/src/fw/paravirt.h b/src/fw/paravirt.h
> index 62a2cd07..b56e96e8 100644
> --- a/src/fw/paravirt.h
> +++ b/src/fw/paravirt.h
> @@ -30,6 +30,7 @@ typedef struct QemuCfgDmaAccess {
>
> extern u32 RamSize;
>  extern u64 RamSizeOver4G;
> +extern u64 RamSizeOver64G;
>  extern int PlatformRunningOn;
>  extern u8 CPUPhysBits;
>  extern u8 CPULongMode;
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index 0395fdbf..1247eb12 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -1197,7 +1197,11 @@ pci_setup(void)
>          }
>      }
> if (CPUPhysBits >= 36 && CPULongMode && RamSizeOver4G) {
> /*
> * Only enable this if we exceed 64G, as some older 32-bit Linux VMs cannot
> * handle the 64-bit window correctly.
> */
> if (CPUPhysBits >= 36 && CPULongMode && RamSizeOver64G) {
>     dprintf(1, "enabling 64-bit pci mmio window\n");
>     pci_pad_mem64 = 1;
> }